[Haskell-beginners] List -> Map -> List, to add duplicates?

[Tom Murphy]

Hi All,
     This seems like an inefficient way to do what I'm trying to do.
I'd really appreciate any suggestions or comments:


import qualified Data.Map as Map

data Currency = Dollar
              | Yen
              | XP
              | Health
              | Street_Cred
              | Peso
    deriving (Show, Eq, Ord) -- why ord?

withDups = [(30, Dollar), (-20, Street_Cred), (-2, Dollar), (30, XP),
(15, Peso), (30, XP)]


flipAssoc (a, b) = (b, a)

noDups = Map.fromListWith (+) (map flipAssoc withDups)

final = map flipAssoc $ Map.toList noDups



Thanks for your time!
Tom